1,720,981 research outputs found
On the frequency carrier offset and symbol timing estimation for ccsds 131.2-b-1 high data-rate telemetry receivers
Full text linkIn recent years there have been significant developments in satellite transmitter technology to follow the rapid innovation of sensors on-board new satellites. The CCSDS 131.2-B-1 standard for telemetry downlink, released in 2012, is part of the next generation of standards that aims to support the increased data-rate caused by these improvements in resolution. As a result of its relative novelty, this standard currently lacks in-depth analysis by researchers, but it is also strongly supported by the European Space Agency (ESA) for future missions. For these reasons, it seems important to evaluate how major receiver sub-components, such as timing recovery and carrier frequency correction, can be designed and implemented in new receivers that support this standard. The timing error detectors (TED) and frequency error detectors (FED) were therefore studied on the specific peculiarities of CCSDS 131.2-B-1 in its usual environment of Low Earth Orbit (LEO). Estimators have been evaluated highlighting performances, trade-offs and peculiarities of each one with respect to corresponding architectural choices. Finally, a receiver architecture derived from the paper considerations is proposed in the aim of supporting very different mission scenarios. Specifically, the realized architecture employs a parallel feedforward estimator for the timing recovery section and a novel multi-algorithm feedback frequency correction loop to efficiently cover both low symbol rates (5 Mbaud) and high data-rates (up to 500 Mbaud). This solution represents a good trade-off to support these scenarios in a very compact footprint by pushing the clock frequency to the FPGA limit. The FPGA resources occupation on a Zynq Ultrascale+ RFSoC XCZU28DR FPGA is 5202 LUT, 4851 FF, 5 BRAM, and 21 DSP for the timing recovery part, while the frequency recovery section occupies 1723 LUT, 1511 FF, 2.5 BRAM and 32 DSP
CCSDS 131.2-B-1 Frequency Estimation Trade-Offs and a Novel Multi-Algorithm FPGA Architecture
No full textIn recent years, following the rapid innovation guidelines of most space agencies, there have been major advances in satellite transmitter technologies. Released in 2012, the CCSDS 131.2-B-1 is one of the most recent downlink standards, with lacking in-depth research, but strongly endorsed by the European Space Agency (ESA). It seems then important to evaluate the performance of different frequency error detectors (FED) on its specific frame structure. This paper firstly deals with the analysis of the most common FEDs, while in the second part it proposes a lightweight architecture to estimate and compensate the carrier error using different algorithms on the same FPGA implementation. Specifically, the Delay Multiply, Kay, Fitz, Luise Reggiannini, Mengali Morelli, and O'Shea et al. estimators are evaluated for both the estimation range and the accuracy. Following the general trade-offs, the design and implementation of the multi-algorithm estimator are detailed for a single feedback loop receiver. The system implements the Mengali Morelli algorithm in the initial acquisition phase to exploit its wide estimation range, while it implements the Fitz algorithm for the tracking phase to take advantage of the lower RMS frequency error. The implementation follows a serial pipelined architecture, which can provide a new estimate for both algorithms in 5205 clock cycles using 942 LUT, 918 FF, 2.5 BRAM, and 7 DSP on a Xilinx Virtex 7 FPGA. Together with the frequency error detector specifications, the entire acquisition and tracking loop is reported, which shows an output RMS frequency error of about 1.05 kHz at 8.5 Mbaud and 50 kHz/s Doppler rate, that can be easily compensated by a common pilot-assisted phase estimator
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Design and FPGA implementation of a high-speed transposed Farrow structure for arbitrary resampling in digital receivers
No full textSample rate conversion is a fundamental operation performed in the digital front-end of software-defined radio and all-digital receivers. Within this context, polynomial-based filters, such as the Farrow structure and its variants, are a sound solution when arbitrary resampling is required. This paper presents a design methodology and the results of the implementation on a field-programmable gate array (FPGA) device for a high-speed transposed Farrow structure based on a novel parallel architecture. The implemented architecture supported an input sample rate of up to 2.184 GHz with moderate utilization of the FPGA resources. Furthermore, signal-to-noise ratio and spurious-free dynamic range values higher than 87 dB and 98 dB were reported over a wide range of sample rate conversion factors. Our results may suggest an improvement in the tradeoff between flexibility, complexity and throughput compared with previous work in the field
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
A Comprehensive Trade-off Analysis on the CCSDS 131.2-B-1 Extended ModCod (SCCC-X) Implementation
No full textFollowing the expansion of the industry requiring small satellites with payloads producing high data rates, the Consultative Committee for Space Data Systems (CCSDS) introduced the CCSDS 131.2-B-1 standard in 2012. The standard combines Serially Concatenated Convolutional Codes (SCCC) with different types of modulation to provide a cost-effective, reliable and efficient payload data transmitter with a high degree of flexibility. This flexibility, due to the number of modulation and coding formats (ModCod), can help designers to better adapt the system configuration to the specific needs of the target. In addition, the use of Adaptive Code and Modulation (ACM) provides the means to adapt payload data transmission to variable channel conditions. To further increase flexibility, the 'EGRET-Next Generation High Rate Telemetry' project has recently defined a proposal to extend the CCSDS SCCC standard to include more efficient transmission schemes. This extension, also called SCCC-X, introduces 10 new ModCods together with a new SCCC-BCH combined encoder and new higher-order modulations (128-APSK and 256-APSK). This document illustrates the entire transmission chain architecture of the SCCC-X telemetry transmitter, highlighting the possible design trade-offs in order to provide a reference for other future developers. Special attention is paid to the analysis of implementation compromises in terms of Bit Error Rate (BER) loss, efficiency, throughput, and source occupation on relevant space-grade FPGAs. In particular, the synthesis results show that SCCC-X can be implemented without changes in the critical path compared to CCSDS 131.2-B-1 and that the implementations are able to achieve more than 450MSym/s on the Xilinx Space-Grade Kintex 7 Ultrascale FPGA and more than 250Msym/s on the Microsemi RTG4 FPGA
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